On The Construction of Aircraft Conceptual Geometry for High-Fidelity Analysis and Design

Abstract

This paper examines the desirability and the challenges of incorporating highdelity geometry de nition into the Multidisciplinary Design, Analysis and Optimization (MDAO) process earlier than currently practiced. A major objective is the ability to enable geometry de nition for lowdelity as well as highdelity analyses, in order to support the entire MDAO process from conceptual to detail design in a seamless manner. Another objective is the ability to support di erent disciplines such as both structural and aerodynamic analyses from the same geometry de nition. Finally, there are the goals of ease of use and support for automation to minimize unnecessary or repetitive human e ort. It is argued that Constructive Solid Geometry (CSG) is the natural foundation for attaining these goals. Two di erent current user-level approaches which employ CSG at low level are considered: 1) CAD systems and their \feature based view of construction, and 2) Bottom-Up methods which generate solid \components. Although Bottom-Up methods do not have the turn-key features of commercial CAD systems, it is clear that their exibility and potential open nature is an advantage in the long term, especially if geometric design-gradient information is required for optimization. To realize the MDAO objectives via the Bottom-Up approach, a new software suite, the Electronic Geometry Aircraft Design System (EGADS), has been developed. It is a relatively simple and compact Open-Source Object-Based API built on top of the extensive OpenCASCADE solid-modeling kernel. EGADS routines implement relatively high-level operations which insulate the user from OpenCASCADE’s size and complexity, and for maximum exibility can be driven by either C, C++, or FORTRAN user applications. The basic features and constructs of EGADS are described, and an example application is presented to demonstrate its capabilities and e ectiveness.